Thanks, I'll give it a go and see if the EM light stays off.
In the mean time I found something rather interesting; I changed the spark plugs and HT leads last month. Bearing in mind I am not a mechanic or even an amateur tinkerer, I'm a novice with a set of spanners, a screw driver and some sockets, I became suspicious that I may have somehow cocked up the spark plug installation. So I had an investigation this afternoon, took the plugs back out and found 2 of them were quite black with sooty deposits. Those two plugs both had the washer (the one that sits between the lip on the plug and the engine) jammed at a slight angle a mm or so away from the lip of the plug, thus; the plug was not screwed properly down onto the engine. I freed up the washers applied a little copper grease between the washer and the lip of the spark plug to hold it in place, and gently put them pack in until finger tight, then torqued them up with the socket wrench.
It occurs to me that if these plugs were not able to ignite the fuel fully, it may have been depositing crud down through the exhaust and into the Cat (same as the crud on the plug).
so I reset the ecu again, but the EM light came straight back on when I drove it some hours later. It always seems to pop back on just as the engine reached operating temperature.
I remembered the code -Catalyst system efficiency below threshold.
Again sorry for the long post, If you read it all the way through I give you express permission to go to the fridge and pour yourself a beer